Chemical process and products



Patented Apr. 15, i94

CHEMICAL PROCESS AND PRODUCTS Maynard S. Raasch, Wilmington, and ClementW.

Theobald, Christiana Hundred, Del., assignors to E. I. du Pont deNemours & Company, Wilmington, Del., a corporation of Delaware NoDrawing. Application April 27, 1944, Serial No. 533,056

7 Claims. 1

This invention relates to new ketones and to a method for theirpreparation. a

This invention has as an object the provision of new ketones. A furtherobject is the provision of new cyclopentenones. A still further objectis the production of 3- and 3, 4-substituted cyclopentenones. It is alsoamong the particular objects of this invention: to provide 3-alkylsubstituted cyclopentenones; to provide 3,4-alkyl substitutedcyclopentenones; to provide 3-alkoxy substituted cyclopentenones; toprovide 3,4- alkoxy substituted cyclopentenones; and to provide 3-methyland 3,4-dimethyl cyclopentenones. Still further objects reside in.methods for obtaining the above mentionedketones. Additional objectswill become apparent from an examination of the following descriptionand claims.

These and other objects and advantages are accomplished according to theherein described invention which broadly comprises heating, unders'uperatmospheric pressure and at a temperature within the range of from125 C. to 250 0., carbon monoxide in contact with a substituted butadiene-1,3 having the general formula.

wherein the A substituent is selected fromthe group consistingof alkyland alkoxy radicals and the B substituent is selected from the groupconsisting of hydrogen atoms and alkyl and alkoxy radicals, saidsubstituted butadiene-1,3 being dissolved in an inert organic solventcontaining an acidic material whose acid ionization constant is lessthan 2X10, the reaction mixture having a pH within the range of fromabout 2 to about 6.

In a-more restricted embodiment this invention comprises heating, undera pressure exceeding 500 atmospheres and at a temperature within therange of from 180 C. to 220 0., carbon monoxide in contact with asubstituted butadiene-1,3 having the general formula 2 CnH2n+1COOHwherein n is a number selected from the group consisting of 0 andpositive integers within the range of from 1 to 3, the reaction mixturehaving a pH within the range of from about 2 to about 6. r

The novel products of this invention are 3- and 3,4-alkyl and alkoxysubstituted cyclopentenones. In other words, said products arecyclopentenones containing a substituent selected from the'group.consisting of alkyl and alkoxy radicals attached to the B-carbon atomof the cyclopentenone ring and a substituent selected from the groupconsisting of hydrogen atoms and alkyl and alkoxy radicals attached tothe 4-carbon atom of the cyclopentenone ring.

The following examples, in which proportions are in parts by weightunless otherwise specified, are given for illustrative purposes and arenot intended to place any restrictions or limitations on the hereindescribed invention:

Example I A solution containing parts of absolute ethanol, 3 parts ofacetic acid and 41 parts of 2,3- dimethylbutadiene-L3 saturated withhydroquinone, is placed in a silver-lined shaker type autoclave providedwith a high pressure gas inlet and a thermocouple well. The pH of thesolution is 3.9. The oxygen present in the reactor is displaced withnitrogen and carbon monoxide is introduced under 385 atmospherespressure. The temperature of the reaction mixture is raised andmaintained at 200 C. by means of external heating. At this temperaturethe pressure is increased to 850 atms. by the introduction of carbonmonoxide and'gradually raised to 950 atms. during the next hour. Thecarbon monoxide which is being consumed is replaced periodically in sucha manner that the pressure is maintained at 900 to 950 atms. Reaction issubstantially complete after two hours, but the reaction conditions oftemperature and pressure are maintained for 6 hours more.

Upon cooling, the unreacted carbon monoxide is bled off and the reactionproduct is isolated by decanting the supernatant ethanolic solution fromthe insoluble hydrocarbon portion, and subjecting the former todistillation. After removal of ethanol and unreacted diene, the residueis subjected to distillation. The fraction boiling at 73 to 79 C. at 9mm. consists mainly of a ketone with a small amount of a higher boilingdimer of 2,3- dimethy1butadiene-1,3. .This ketone reacts with2,4-dinitrophenyl-hydrazlne to give a derivative melting at 178 to 178.5C. and whose composition is shown by analysis to be C13H14N4O4, which isin accord with the expected composition and properties of a 3,4-dimethylcyclopentenone.

Example: II

A solution containing 80 parts of ethanol, 34 parts of2-methylbutadiene-1,3, 3 parts of acetic acid and 1 part of hydroquinoneis treated as in Example I at 200 C. for 13.5 hours under 820 to 995atms. CO pressure. A pressure drop of 80 atms. occurs slowly during theentire reaction period.

A small amount of polymeric material (1 g. from 34 g. starting material)is removed and the liquid distilled. A small amount of2-methylbutadiene-1,3 and alcohol is removed at atmospheric pressure andthe residue distilled under reduced pressure. A ketonic fraction boilingat 70 to 80 C./40 mm. is obtained. A hydrocarbon fraction boiling at 8'0C./40 mm. is also obtained. The 2,4-dinitrophenylhydrazone of the ketonemelts at 181 to 182 and has the composition Curl-112N404. Anal. Found:C, 52.05%; H, 4.37%; N, 19.6%. Calc. for Ci2H12N4O4; C, 52.17%; H,4.38%; N, 20.28%. The ketone then has the composition CsHaO, whichagrees with that of 3- methylcyclopentenone.

Although the above examples have illustrated the practice of thisinvention with 2,3-dimethylbutadiene-1,3 and 2-methylbutadiene-1,3, itis to be understood that the invention is applicable to any substitutedbutadiene-1,3 having the general formula wherein the A substituent isselected from the group consisting of alkyl and alkoxy radicals and theB substituent is selected from the group consisting of hydrogen atomsand alkyl and alkoxy radicals, Specific examples of such dienes, inaddition to 2,3-dimethylbutadiene-1,3 and 2- methylbutadiene-1,3 are2-ethylbutadiene-l,3; 2-propylbutadiene-l,3-; 2,3-dimethoxybutadiene-1,3; 2,3-diethoxybutadiene-1,3; and the like.

In the practice of this invention there can be used temperatures rangingfrom 125 to 250 C. and pressures above atmospheric to a maximumdetermined by the practical limitations of the reaction vessel. It ispreferred, on account of the superior yields thereby obtained, tooperate at temperatures within the range of from 180 C. to 220 C. and atpressures in excess of 500 atmospheres.

The process is operated in the presence of an inert organic solvent suchas an aliphatic alcohol, dioxane, benzene, and the like. The aliphaticalcohols and especially the lower aliphatic alcohols are the preferredsolvents. For best results the concentration of the diene in thesolution should be between 25% and 75%, by weight, althoughconcentrations outside this range can be used if desired.

Any acidic material having an acid ionization constant less than 2x10can be used in adjusting the pH of the reaction medium. However, onaccount of the superior yields had therewith, the preferred acidicmaterials are carboxylic acids having the general formula CnH2n+iCOOHwherein n is a member selected from the group consisting of and positiveintegers, and especially the lower aliphatic monocarboxylic acids suchas formic, acetic, propionic, butyric, and the like. In general, anamount of acid is used to give a pH in the reaction medium of from 2 to6.

The use of a polymerization inhibitor for the diene is not essential tothe practice of this invention. It is desirable, however, .to add such amaterial since the yield of desired product is increased thereby byprevention of loss of diene through conversion to undesiredpolymerization products. In the preferred practice, therefore, thereaction is carried out in the presence of a polymerization inhibitor.Specific examples of such materials, in addition to hydroquinone, arephloroglucinol, catechol, phenol, and the like.

The process of this invention provides an easy and practicable methodfor preparing novel ketones, The reactions involved in theaforementioned process may be represented below. For convenience ofillustration the reaction is presented for the conversion of2,3-dimethylbutadiene to a 3,4-dimethylcyclopentenone.

As hereinbefore stated, the novel products of this invention are 3- and3,4-alkyl and alkoxy substituted cyclopentenones. Included amongexamples of said substituted cyclopentenones are:3,4-dimethylcyclopentenone, 3-methylcyclopentenone;3-ethylcyclopentenone, 3-propylcyclopentenone,3,4-dimethoxycyclopentenone, 3,4-diethoxycyclopentenone, 3methyl-4-methoxycyc1opentenone, and the like.

The substituted cyclopentenones of this invention are useful assolvents, and as intermediates in the synthesis of other organicproducts, such as resins, perfumes, secondary alcohols and dibasicacids.

As many apparently widely difierent embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that We do not limit ourselves to the specific embodimentsthereof except as defined in the appended claims.

Having described the present invention, the following is claimed as newand useful:

1. The process for obtaining a substituted cyclopentenone, whichcomprises heating, under superatmospheric pressure and at a temperaturewithin the range of from C. to 250 (3., carbon monoxide in contact witha substituted butadiene-l,3 having the general formula wherein the Asubstituent is an alkyl radical and the B substituent is selected fromthe group consisting of hydrogen atoms and alkyl radicals, saidsubstituted butadiene-1,3 being dissolved in an inert organic solventcontaining an acidic material having an acid ionization constant of lessthan 2 10 the reaction mixture having a pH Within the range of fromabout 2 to about 6.

2. The process for obtaining a substituted cyclopentenone, whichcomprises heating, under a pressure exceeding 500 atmospheres and at atemperature within the range of from 180 C. to 220 0., carbon monoxidein contact with a substituted butadiene-1,3 having the general formula ti HzC=C-C=CH2 wherein the A substituent is an alkyl radical and 6 the Bsubstituent is selected from the group con- 6. The compound,3,4-dimethyl-A -cyclcpensisting of hydrogen atoms and alkyl radicals,said tenone having the structural formula substituted butadiene-1.3being dissolved in an alcohol having the general formula CnH2n+l0H f=wherein n is a positive integer within the range 5 H:C\ H,

of from 1 to 4, said alcohol containing an acid having the generalformula CnH2n-i-1COOH where- II in n is a number selected from the groupcon- 0 sisting of 0 and positive integers within the range The 0 mm 3mem 3 C10 ntenme of from 1 to 3, the reaction mixture having a 10 havingggf formula. y pe pH within the range of from about 2 to about 6.

3. The process for obtaining 3,4-dimethylcyclo- HC=(;JCHI pentenone,which comprises heating, under a 5 pressure exceeding 500 atmospheresand at a temperature within the range of from 180 C. to 220 H 0., carbonmonoxide in contact with 2,3-dio methylbutadiene-l,3 dissolved inethanol containing acetic acid, the reaction mixture having MAYNARDRAASCH' a pH within the range of from about 2 to about 6. CLEMENTTImOBALD' 4. The process for obtaining B-methylcycloo pentenone, whichcomprises heating, under a RWERENCES CITED pressure exceeding 500atmospheres and at a The following references are of record in thetemperature within the range of from 180 C. to file of this patent: 2200., carbon monoxide in contact with 2- mm mm methylbutadiene-1,3dissolved in ethanol contain- STATES PA ing acetic acid, the reactionmixture having a Number Name Date pH within the range of from about 2 toabout 6. 1,973,662 Schalch sept- 1934 5. A cyclopentenone having thegeneral for- OTHER REFERENCES mula AC=C-B Chemical Abst., vol. 7, page3113 (1913) Ab m i stracting an article by Godchob in Comptes rendues156, pp. 1779-81. I Chemical Abst., vol. 8, page 1285 (1914) Ab Astracting article by Willstatter in Berichte t7,

wherein A a an aikyl radical and B is of the group consisting ofhydrogen atoms and alkyl radicals.

